Project Overview

ERGO were commissioned to undertake intrusive investigation, remediation and validation of a proposed executive apartment block complex in Gateshead, England. Several rounds of investigation and partial grouting of the site historically provided an inconsistent remediation strategy. ERGO were able to bring all the historic reports together, into one document, to determine the further works required and the overall Remediation and Enabling Works Strategy.

Site Background

The site was a derelict plot of land with the remains of a former partially demolished building located in the north of the site and was overgrown with self-seeded vegetation. An active railway line extends roughly east to west immediately beyond the eastern site boundary. Stockpiles of large sandstone blocks were present across areas of the site. Previous investigation had recorded elevated heavy metals and PAHs within the previously turned over top 2 metres of the site. Partial grouting had been completed but some areas were inaccessible at the time, including beneath the sandstone block stockpiles and the existing structure.

Site Works

ERGO completed additional investigation to assess the extent of contamination and investigate the presence or absence of a historically marked mine shaft. Following this, a Remediation & Enabling Works Strategy was produced to include delineation, excavation and validation of identified contamination, demolition of the existing structure, additional grouting across the site, removal of further obstructions and placement of a clean cover system within proposed landscaping areas.

ERGO also completed an earthworks assessment model for the site with a CL:AIRE Materials Management Plan to facilitate the reuse of materials onsite where suitable, and the importation of clean materials to be placed in landscaping areas. An updated Coal Mining Risk Assessment and Grout Specification were completed by ERGO, detailing the depth of previously treated workings, highlighting areas where further grouting was required and specifying the depth and spacing of the treatment.

Throughout the remediation process, ERGO also assisted with the design of pile mats, scaffold mats, plate load testing, watching brief during elements of the works and regular liaison with regulatory bodies including Gateshead Council and Network Rail.

Key Issues and Solutions

The site is located adjacent to Network Rail infrastructure, which adds additional checks and considerations to activities and proposals on site. Due to the recorded former mining activity on site, pile design depth had to consider the treated mineworkings. A low access bridge was present at the site entrance, limiting the plant available to complete the works. The other main issue was the inconsistency of historical information. Therefore, some remediation techniques were recommended across the site to ensure no areas were missed.